Solid-Phase Assay Procedures
Solid phase assays have been used to determine the presence and/or amount of substances such as proteins, peptides, carbohydrates, lipids and small molecules in a variety of biological samples (e.g., blood, serum, urine, saliva, tissue homogenates). The solid phase is used to separate molecules that bind to the solid phase from those that do not. Small beads are generally used as the solid phase to capture the analyte. However, in conventional procedures, it is difficult to perform a multiplicity of assays in a single sample at about the same time (multiplex assay).
One approach that has been taken in order to increase the scope of the multiplex assay is to use transponders associated with the solid phase beads to index the particles constituting the solid phase (see, for example, U.S. Pat. No. 5,641,634, WO 97/20074). A diagrammatic representation of the system for use in detecting DNA sequences is disclosed is shown at pharmaseq.com/illustration.html. The transponder has a photovoltaic cell as its power resource through light or laser (column 5, line 50-65; FIG. 6). A laser is used to activate the light cell and supply the power. The transponder then emits a radio signal. This can be a weakness.
Radiotags or transponders have also been used in combinatorial chemical approaches (reviewed in Service, 1995, Science 270:577). In one approach, a radiofrequency (RF) encodable microchip is coupled with a polypropylene capsule of derivatized polystyrene resin so that a radioscanner registers the identity of a capsule and the contents of each beaker it enters (see, U.S. Pat. Nos. 5,777,045 and 6,051,377 and Moran, et al., 1995, J. Amer. Chem. Soc. 117:10787-10788). The data is uploaded to a computer that keeps track of the order of addition to monomers to the capsule.
In another approach by Nova et al., the data obtained is actually stored on the microchip itself, using a transmitter that writes the information to the chip (see, for example, U.S. Pat. Nos. 5,741,462, 5,751,629, 5,874,214, 5,925,562 and 6,025,129). The data is not uploaded to the computer until the run is complete. Therefore the system disclosed comprises a recording device and storage unit. It has been suggested that this system may also be used in immunoassays and hybridization reactions and to detect macromolecules, to identify receptor bound ligands, and cell sorting.
RFID
A radio frequency identification system (RFID) carries information in suitable transponders that contain tags having information. The information on the tags is retrieved in response to a radio signal by machine-readable means (for a review of RFID, see www.aimglobal.org)
A basic RFID system contains the following three components:
(a) an antenna or coil
(b) a transponder programmed with unique information
(c) a receiver which decodes the unique information
The antenna, which acts as a conduit between the transponder and receiver, emits radio signals to activate the tag on the transponder and read and write information to it.
The transponder contains a tag, which responds to a signal for the information it generated. It should be noted that the terms “transponder” and “tag” are used interchangeably in the art. The transponder or tag logic may be read-only or random access.
The receiver receives the information transmitted by the transponder and decodes it. The information may further be processed.
It has been suggested that RFID can be used in transportation and logistics, manufacturing and processing security, animal tagging, waste management, time and attendance, postal tracking airline baggage reconciliation and road toll management.